Home » GB9074.4-1988 Phillips Pan Head SEMS Screws - Steel (4.8) - Bright Zinc Plated

GB9074.4-1988 Phillips Pan Head SEMS Screws - Steel (4.8) - Bright Zinc Plated

GB9074.4-1988 Phillips Pan Head SEMS Screws – Steel (Class 4.8) – Bright Zinc Plated

FULLERKREG supplies GB9074.4-1988 Phillips pan head SEMS screws manufactured from low carbon steel A3, heat-treated to strength class 4.8, with a bright zinc plated surface finish. Each screw ships with a pre-assembled flat washer (GB9074.24) and a spring washer (GB9074.26), permanently captivated on the shank — eliminating loose washer handling on the assembly line.

What are Phillips Pan Head SEMS Screws?

SEMS screws (also called combination screws or pre-assembled screws) are fasteners in which one or more washers are permanently captured on the screw shank before threading. The washer(s) are assembled onto the blank shank and then the thread is rolled, making the outer diameter of the thread larger than the inner diameter of the washer — so the washer can never fall off during handling or installation.

GB9074.4-1988 defines the Chinese national standard for cross-recessed (Phillips) pan head combination screws with pre-assembled spring washer and plain washer. The assembly is expressed as:

GB9074.4 = GB818 (Pan Head Screw) + GB9074.24 (Plain Washer) + GB9074.26 (Spring Washer)

The pan head profile provides a broad, low-profile bearing surface for excellent load distribution across the clamped material. The Phillips (cross-recessed) drive enables fast, reliable torquing with standard power tools and is well-suited to automated assembly environments.

Benefits of Using Phillips Pan Head SEMS Screws

  • Eliminates loose washer handling — washers are permanently captivated; no separate picking, placing, or alignment required during assembly.
  • Faster assembly — one part replaces three; dramatically reduces cycle time in high-volume production lines.
  • Reduced risk of missing washers — captive design prevents washer omission errors that can cause field failures or warranty claims.
  • Space-saving installation — the shortened unthreaded shank allows clamping of thinner panels; minimum clampable thickness is approximately half that of standard combination screws.
  • Compatible with legacy JIS washer dimensions — flat washer and spring washer conform to GB9074.24 / JIS dimensions, ensuring drop-in compatibility with existing designs.
  • Suitable for automated feeding — consistent geometry and captive washers make these screws ideal for vibratory bowl feeders and robotic assembly systems.
  • Anti-loosening — the pre-assembled spring washer provides continuous axial load to resist vibration-induced loosening in service.
  • Cost-effective general fastening — class 4.8 low carbon steel with bright zinc plating offers an economical solution for non-critical structural and panel fastening applications.

Material & Finish

Component Material Surface Treatment Strength / Grade
Screw Body Low Carbon Steel A3 Bright Zinc Plated Class 4.8
Plain Washer (Flat) Low Carbon Steel Bright Zinc Plated —
Spring Washer Carbon Steel Bright Zinc Plated —

Bright Zinc Plating provides a clean, shiny metallic appearance with good corrosion resistance for indoor and light outdoor applications. Typical salt-spray resistance: ≥ 48 hours to white rust. Suitable for general industrial and consumer product assembly where a cost-effective finish is required.

Dimensional Data – GB9074.4-1988 Phillips Pan Head SEMS Screws

Thread range: M3 – M8  |  Length range: 5 mm – 50 mm  |  Drive: Phillips (Cross Recessed, Type H)

Thread (d) Pitch (mm) Head Dia. dk (mm) Head Height k (mm) Drive No. Min. Clamp Thickness (mm) Max. Clamp Thickness (mm) Unit Weight (g/100 pcs)*
M3 0.5 5.6 2.0 PH1 0.5 varies by length ~38
M4 0.7 8.0 2.6 PH2 0.6 varies by length ~95
M5 0.8 9.5 3.3 PH2 0.8 varies by length ~185
M6 1.0 12.0 3.9 PH3 1.0 varies by length ~320
M8 1.25 16.0 5.0 PH4 1.2 varies by length ~750

* Unit weight is approximate for a representative length (e.g., 16 mm). Actual weight varies by length. Contact FULLERKREG for exact weight data per SKU.

Dimensions of Pre-Assembled Washers

The flat washer conforms to GB9074.24 dimensions. The spring washer conforms to GB9074.26. Both washers are permanently captivated on the screw shank prior to shipment.

Flat Washer Dimensions (GB9074.24)

Thread (d) Inner Dia. d1 (mm) Outer Dia. d2 (mm) Thickness h (mm)
M3 3.2 6.0 0.5
M4 4.3 8.0 0.8
M5 5.3 9.0 1.0
M6 6.4 11.0 1.6
M8 8.4 15.0 1.6

Note: GB9074.24 plain washer outer diameters are slightly smaller than DIN 125A equivalents, optimized for the SEMS captive assembly process.

Spring Washer Dimensions (GB9074.26)

Thread (d) Inner Dia. d1 (mm) Outer Dia. d2 (mm) Thickness s (mm) Height h (mm)
M3 3.1 5.1 0.8 1.6
M4 4.1 6.8 0.9 1.8
M5 5.1 8.2 1.2 2.4
M6 6.1 9.9 1.6 3.2
M8 8.1 13.0 2.0 4.0

Product Images

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Applications

GB9074.4-1988 Phillips pan head SEMS screws in class 4.8 / bright zinc plated are widely used in cost-sensitive, general-purpose fastening applications:

  • Consumer electronics & appliance panels — thin sheet metal enclosures, decorative faceplates, and access covers where a clean bright finish is desired
  • Furniture & fixture assembly — flat-pack furniture, shelving units, and retail display fixtures requiring fast, reliable fastening
  • Structural assemblies — equipment frames, mounting brackets, and general sheet metal fabrication
  • HVAC & ductwork — duct panels, air handling unit covers, and ventilation equipment housings
  • General industrial machinery — guards, covers, access panels, and junction boxes in light-duty industrial environments
  • Automated assembly lines — captive washer design is ideal for robotic and vibratory-feed assembly, reducing part count and handling errors
  • Lighting & electrical enclosures — panel boards, distribution boxes, and light fixture mounting where a bright finish complements the product aesthetic

Particularly suited for applications where panel thickness is limited and an economical fastening solution is required. The class 4.8 strength grade is appropriate for light-to-medium clamping loads in non-safety-critical assemblies. Refer to the dimensional table for minimum clampable thickness per size.

Why FULLERKREG?

  • 🏭 Direct manufacturer — full control over material sourcing, heat treatment, and surface finishing
  • 📐 Standard-compliant — manufactured and inspected to GB9074.4-1988 with full dimensional traceability
  • 🌍 Global supply — export packaging, English documentation, and worldwide logistics support
  • 📦 Bulk & wholesale ready — available in bulk bags, boxes, or custom packaging for OEM and MRO customers
  • 🔬 Quality assured — incoming material certification, hardness testing, and salt-spray testing available on request
  • 💬 Engineering support — custom sizes, materials, and special specifications available; contact our technical team for non-standard requirements

For custom specifications, non-standard sizes, or volume pricing, please contact the FULLERKREG team directly.

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